Interferon lambda signaling in neutrophils enhances the pathogenesis of <i>Bordetella pertussis</i> infection

Interferon lambda plays diverse roles in bacterial infections. Previously, we showed that interferon lambda is induced in the lungs of Bordetella pertussis-infected adult mice and exacerbates inflammation. Here, we report that mice lacking the interferon lambda receptor 1 specifically on neutrophils (MRP8creIFNLR1fl/fl mice) exhibit reduced lung bacterial load and inflammation compared to wild-type mice during B. pertussis infection. In B. pertussis-infected wild-type mice, lung type I and III IFN responses were higher than in MRP8creIFNLR1fl/fl mice, correlating with increased lung inflammatory pathology. There was an increased proportion of interferon gamma-producing neutrophils in the lungs of MRP8creIFNLR1fl/fl mice compared to wild-type mice. IFNLR1-/- neutrophils incubated with B. pertussis exhibited higher killing compared to wild-type neutrophils. Treatment of wild-type neutrophils with interferon lambda further decreased their bacterial killing capacity and treatment of wild-type mice with interferon lambda increased lung bacterial loads. Contributing to the differential killing, we found that IFNLR1-/- neutrophils exhibit higher levels of reactive oxygen species, myeloperoxidase, matrix metalloproteinase-9 activity, neutrophil extracellular traps, and interferon gamma secretion than wild-type neutrophils, and inhibiting NADPH oxidase inhibited bacterial killing in IFNLR1-/- neutrophils. B. pertussis-induced interferon lambda secretion and IFNLR1 gene expression in mouse and human neutrophils and this was dependent on the bacterial virulence protein pertussis toxin. Pertussis toxin enhanced bacterial loads in wild type but not in MRP8creIFNLR1fl/fl or IFNLR1-/- mice. Thus, pertussis toxin disrupts neutrophil function by enhancing type III IFN signaling, which prevents neutrophils from effectively clearing B. pertussis during infection, leading to higher bacterial loads and exacerbation of lung inflammation.